com. But, if it is too restrictive for the required flow, the material will react and blush will appear. 0: l. For example, injection speed may need to be adjusted to counteract splay created by shear stress, which can be caused by the shape of the part. If you turn on the spigot to a garden hose, you will hear a hissing sound at the nozzle end for the first few seconds. Source: Author jmoutoux. Follow Us:Although injection molding is one of the most cost-effective manufacturing options, it does have one drawback. RESPONSIBILITIES: To run product produced by injection molding presses. , flash and short shots, packing and cooling related defects i. Injection Molding The process of forming a material by forcing it from a heated cylinder, under pressure, through a spruce into a cavity of a confined mold. Take a look at five factors in the injection. Set a higher clamping presure. remove the plate suction tube damaged → replace the damaged suction tube or repair. Available for Subscriptions. plastics technology-recent developments and trends. Injection can be profiled by dividing the shot size by 6, and setting up the position profiles to equal segments. Flow lines are off-color lines, streaks, and other patterns that appear on the surface of a part. Moisture is a major. 160"). Multiple gating, higher flow rates, and gate resizing along with higher material temperatures, may improve merging, move lines to non-cosmetic locations, or provide more uniform cooling temperatures to bring materials together before solidification. First-stage injection fills 92% to 99. Remedies: Mold design: (1) Add an exhaust system to a place where the exhaust gas is easily generated. A3:Adjust the ejection pressure to the appropriate state. Sink Marks. A Guide To Polyolefin Injection Molding Introduction Polyolefins are the most widely used plastics for injection molding. The cold slug well received that plug of solidified plastic on the next shot. Tel: (60) 3 7890 6399 9am – 6pm (Mon. Low Gloss. COC retain mechanical properties over multiple regrind cycles. Gas Marks Defined. Injection Molding Know How. 3. This three-part series in the Troubleshooter column outlines key signs used to evaluate splay conditions. 2K. Thermal expansion in the sprue bushing can hold the mold open and cause flash to develop. These are cosmetic blemishes on the part’s surface. Tatjana Geminger, Stefan Jarka, in Specialized Injection Molding Techniques, 2016. cgnx_pdf Download Consumer Products Solutions Guide. It may not necessarily produce visible splay, as the water is consumed in the hydrolysis reaction. The material pumped out of the cylinder is foamed and shows blisters on the injection molding parts surface. It usually appears at the gate where the plastic enters the mold. Large SizeElectric Servo Drive Injection Molding Machine. The inject speed needs to be reduced on the molding machine. 2. The product may be locally pressed on the side wall, so it is easy to scratch the product side surface during mold ejection. Increase the mold temperatures: Cold mold walls prevent material flow. Injection molding problems MOISTURE RELATED DEFECTS Splay Irregular Moldings Brittleness Bubbles Sink Marks There are several methods for drying resins which utilize industrial drying systems prior to injection molding. Bob Hatch is manager of technical service and customer support for Prime Alliance, the Des Moines-based resin distributor. This cosmetic defect occurs in plastic injection molding, when silver or white str. In some cases, hot manifolds may be. Thick sections take longer to cool than thin ones. 2. Garrett MacKenzie is the owner/editor of plastic411. Depending on the material,. 002'') pathways on the shutoff area of the cavity blocks. In thermoplastic injection molding, the mold is always said to be “cold”—that is, relative to the temperature of the plastic melt. When gases get trapped during mold filling, high pressures can cause ignition, which leads to the plastic burning. The cost of injection molding is in three places, cycle time, mold construction, and setup costs. Most often this problem occurs when parts are being made with colored, semi-transparent resins, or have. The root cause of sink marks is a difference in cooling time between the. If it’s a void, the wall stock will collapse and show a sink. Reporting to Shift Supervisor, the successful candidate will operate Molding presses and related equipment for the purposes of fittings production. Ensure Machine Purging: In injection molding, purging refers to cleaning the molding machine of one material or color. 3. Understanding your surface requirement is very important, as sometimes it’s. metal injection moulding 7. Receive a 10% discount on Injection Molding Principles and Injection Molding Troubleshooting if registered for both workshops. Here is a look at a few more surface finish considerations for making better molds. Splay is a cosmetic defect that occurs in plastic injection molding, when black or white streaks appear on the surface of this part. Preventing Flash in Injection Molded Parts. Injection Molding Flash Remedies. Optimize temperature settings of the molding machine to avoid material degradation. A cosmetic defect, it is often silvery in color and is sometimes called 'silver streak'. 5. 2 mm and a ring movement of at least 4. Splay due to moisture usually results in silver streaks on the surface and slight delaminating of a film layer. Learn more about Injection Molding in the Injection Molding Know How section. Though it is only visible once plated, it is caused my molding issues; trapped moisture in the plastic can come to the surface during. The cure for splash marks is，therefore to eliminate all volatile matter. He has provided analytical services to material suppliers, molders, and end users for the last 10 years. Specific attention to processing details will enhance quality and productivity . I give you 4 different variables that can cause splay. Simplified diagram of the process. Splay Silver-streaked appearance caused by gasses in. Scribd is the world's largest social reading and publishing site. Hold time. View my complete profile. In that case, the material particles. Sink marks usually occur when there’s a shrinking of a molded component’s inner part. The chart below shows recommended wall thicknesses for common injection molding resins. High nozzle temperatures can promote the formation of thermal splay marks from keeping the. A material that will undergo or has undergone a chemical reaction by the action of heat and pressure, catalysts, ultra-violet light, etc. The Society of the Plastics Industry [spi] PDF Price. There are three ways to mold. Contamination can be defined as an imperfection in a molded part caused by the presence of a foreign object or material that is not part of the original molding compound. Sinonim splay dan terjemahan splay ke dalam 25 bahasa. Stiff materials can utilize deeper vents. About the Author: Robert Gattshall has more than 22 years’ experience in the injection molding industry and holds multiple certifications in Scientific Injection Molding and the tools of Lean Six Sigma. mold design 4. Usually, the rising temperature of the mold. A component of the injection-molding machine wherein the resin pellets are melted, compressed and injected into the mold's runner system. 008 to 0. . Appearance alone cannot tell you which type of splay is present. 375 inch; shorten the gate land to no. At this temperature,. Learn about 10 common plastic injection molding defects, find out why they occur, and get tips to fix them. The best way to avoid these part defects is to work with a plastic injection molder that has a great deal of experience with various resins and their applications. Injection molding is a process that utilizes a molten material that is forced into a mold to form a part. FIG. This type of injection plastic defect occurs as small depressions or recesses. Flow marks are caused by a variety of factors in the injection molding making technology, and they happen at the gate. He is a highly respected writer and educator in the area of plastics processing. Switch to a hot runner or reduce the size of the main channel. Injection moulding process explained with key elements. 1. Plastic injection molded parts can be surface finished from matte to highly polished. Tel: (60) 3 7890 6399 9am – 6pm (Mon. Faster, and even more accurate, the J-ADS Series assures the highest levels of. Injection molding BrE or Injection molding AmE, is a manufacturing process for producing parts by injecting molten material into a mold. 3. Clamp tonnage / High pressure is too low. Educalingo cookies are used to personalize ads and get web traffic statistics. Here are a few of the most common defects that may occur in plastic injection molding — and how product teams can avoid them. High injection speeds lead to shear splay since the material is exposed to high shear conditions. 14 billion, up 12. Injection molding offers numerous advantages when it comes to producing HDPE parts, such as cost-effectiveness, high customization, and high malleability. Even without any injection molding surface finish or post-processing treatment, molded. One of the most significant advantages of injection molding is the natural surface finish of molded parts. Molding Equipment Vi-Chem PVC's can be molded on standard injection molding machines. While at the machine, you will be shown basic standard set-up parameters & techniques and how to properly operate the injection molding machine. Office: +1. When in the hands of inadequate expertise, a lot can go wrong. 102-106; bibl. Splay can be caused by a variety of variables, and recognizing these sources is critical for resolving and preventing the issue. When purchasing plastic injection molded parts. 3. The pressures used to inject molten plastic is tremendous. One significant processes utilized to produce plastic pipe fittings is the injection molding. Learn more about how to identify and deal splayCalculate melt residence time by formula in molding guides . spe western sections annual pacific technical conference and technical displays/1979/costa mesa ca; usa; da. Splay – Contamination – Cold Slugs (discontinuities where injected material was inconsistent)Causes & Solutions for this injection molding defects: 1. The melt holds enough temperature to maintain a low enough viscosity. 1 Caused By The Quality of Injection Mold. Flow marks caused by chaotic jet flows. . ( splā) 1. This quiz was reviewed by FunTrivia editor crisw before going online. 375 inch; shorten the gate land to no. Haze develops when PET in either injection or blow stages is heated beyond about 115°C (240°F) and allowed to cool down for even a short time. Preventing the polymer surface from instantaneously freezing during filling allows the material to. Splay is sometimes called "silver streaks". Increase the mold temperature and reduce the barrel temperature for injection molding of thin-walled products. Splay can be a costly problem in the production of your molded components. Moisture and shear are the two primary causes of splay on an injection molded part. Splay is a term used in the manufacture of injection molded plastics to refer to off. The optimum fill time was 2. This standard provides a thorough procedure to help develop a robust and stable injection molding process that has minimal variation and produces a high-quality plastic part. Answer: The trapped gas ignites from the heat generated by pressure. Add vents in local areas that show blush. The shape is a part metal square (typically steel or hardened steel) that is machined to frame the depressions in the square. This is an excerpt from Lesson #6 in Paulson's Injection Molded Part Problems and Solutions training progam - Splay (or Silver Streaks) and how to fix them. Bubbles can affect the strength of the part and may create cosmetic defects. Injection Molding Process. Problem: Shear-sensitive material; gate land length much too long; and barrel temperatures, in an effort to eliminate gate blush, were raised too high. Place the heated probe into the melt puddle (Purging mass). Method of switchover from first to second stage. It can be difficult to. To determine the cause of your issue, first determine where. Adjust the thickness (1t-2t) 6. Molding Problems Trouble Shooter. When a rust preventative is over-applied, it can cause grease to break down in certain areas of the mold, leading to bleeding. Splay (also called chicken tracks, tails, and hooks) is usually caused by a gas, usually water (steam), but can be caused by unmelt, dirt, chips, or flakes from three-plate molds, cold slugs, excessive volatile additives, air, and/or decompression. Remedies: Raise the mold temperature in increments of 10 degrees F until the bubbles disappear. There are many "lookalike" defects, and plenty practicable causes of splay, including excessive mold lubrication. Polypropylene is easy to mold despite its semi-crystalline nature, and it flows very well because of its low melt viscosity. Therefore injection mold core and cavity surface finish are as per the specified part drawing. Garrett MacKenzie | Mar 12, 2023 In the injection molding process, the. The higher requirement on the surface finish of the part, the longer effort and time spent during the production of the mold, hence it will lead to higher cost on your overall cost. This allows the melt to keep enough velocity to ensure proper filing. Make the injection speed lower; Debris in the. Splay be ampere cosmetic flaw that occurs in plastic injection molding, when silver or white streaks seem on the surface concerning aforementioned part. i-Moulder injection molding defects and remedies problem solving guide and indicates typical methods for fine tuning the plastic injection moulding machine to reduce the occurrence of common molding problems including:-. 025 inches per inch, depending on the particular resin, molding conditions, part design, part wall thickness, and direction of flow. What Are Silver Streaks in Injection Molding? A silver streak, also known as a splay mark, is a cosmetic defect that is typically visible on plastic parts with a smooth surface. It owns the name silver streak. Thermoplastic resins fall into two distinct categories, each with their own advantages and disadvantages. This manual, A Guide to Polyolefin Injection Molding, contains general information concerning materials, methods and equipment for producing high quality, injection molded, polyolefin products at optimum production rates. COCs low shrinkage, lubricated grades and mold. The forums offer a method to ask colleagues directly. Together, they have published a book, available on Amazon, that is a. fFlow rate. Here are some common fixes for injection molding splay: Moisture-related: Ensuring that all material is thoroughly dry before beginning the injection mold process is crucial. Lets discuss moisture, as most of the time splay occurs because the resin has not been properly dried. In fact, viscosity is influenced more by shear rate—injection speed—than temperature or even resin lot variations. 3. The viscosity of the plastic being molded determines the depth of the vent. Welds. What's SPLAY in molding & how to fix it. sales@uninko. Allows you to accommodate a variety of part sizes. Content Provider. To fix it, you can try increasing the injection speed, adjusting the temperature of the barrel, increasing the back pressure, or using a different type of plastic material. That’s the air escaping out of the nozzle until the hose is full of pressurized water. the following below are explained 1. If the only solution is to use a spray, try our Tuff-Kote and Dri-Kote high-performance mold-release sprays. conventional injection molding equipment. Splay or streaking is often a silver color and may look like mica. cellular injection-molded parts with dynamic mold temperature control”. Our quality software enables us to provide the molders with data on the specific defects and where we are seeing them on the parts so they can make adjustments to their processes and/or modifications to the molds themselves to solve the problems. It is made from stainless steel. 07% can cause cosmetic problems on a part surface if the material is exposed to the temperatures of melt processing. The gate restricts flow as the part fills. Synonimy słowa splay i jego tłumaczenie na 25 języków. S. Moisture and shear are the two primary causes of splay on an injection molded part. proposed that surface defects, such as splay marks and silver streaks, are. The mold leaks oil, water, and air into the mold cavity, which easily causes silver streaks on the part surface. Remedies: Decreasing the barrel temperature allows the plastic to stay molten without burning or charring. Splay Marks. Pipe fitting injection molding process. Possible Causes & Remedies: Machine Cause. In any case, you’d prefer to create polycarbonate parts of different sizes; then this is the best technique that you need to use. (2) Increase the size of the runner system. Focus more on the ejection mechanism in the mold design to reduce or eliminate the dependence on mold release agents. 4. There are many "lookalike" defects, and many possible causes of splay, in excessive mold lubrication. Splay. 5:1 and 3. Injection Molding. Let’s first discuss moisture, as most of the time splay occurs because the resin has not been properly dried. Excessive ash content. Teach continue info how to identify and handle splayThese materials tend to generate higher surface resistance during the molding process, creating drag and turbulence that may be reflected in the part appearance—glass fibers, for instance, can add a stringy or sparkly finish to a textured part, while flame retardants might lead to the whitish streaks known to plastic injection molders as splay. At times the part may also shatter. Remedies: Although it may impact the manufacturing cost, the way. Back Pressure in an injection molding process is often defined as “the resistance of the screw to recover as the metering section pumps molten plastic through the non-return valve to the. It is these steam bubbles that you see as Splay. Grippers for Injection Molding; Chemical for Injection Molding. Figure 2 is a part tested a few minutes after molding and Fig. Splay is a cosmetic defect that occurs when moisture gets into the resin during the heating process of the injection molding machine. Verify that the process itself has been decoupled first, yielding a 95-98% full part with no hold or pack added. An opening in the mold where the injection-molded material enters the mold to create the intended plastic part. Most drying specifications for various resins are at temperatures where the resin will not agglomerate,If a balance tool is creating unequal short shots, make sure drops and tips are not contaminated from a previous run. Molding moist polycarbonate can cause splaying, while reducing the polymer’s impact and tensile strength. These injection mold coatings are applied either in your tool room or on the press and give exceptional release characteristics to the part in the mold, allowing it to eject without sticking and thereby eliminating any pin push marks. 39 sec, is about 2000 psi-sec. Usually oblong, silvery surface streaks which are open in the shapre of a U counter to the direction of flow. Knit / Weld Lines. The linear mold shrinkage of injection molded parts will vary from 0. Tool: Single-cavity, cold runner. [1] The most common cause of splay is moisture, which is caught in the resin inside the injection molding machine. 2. How do you reduce splay in injection molding? A large drop in temperature when material enters the mold from nozzle can lead to beginning-of-fill splay. Splay – visible gray or silver streaks on the finished product caused by excess moisture in the material;Injection-molded plastic parts replicate the Injection mold surface finish (Refer to SPI Surface Finish Chart). It offers ways to identify splay causesm and gives solutions on how to correct splay c. The main types of injection molding defects are: 1. Increase the venting: Ventilation supplies better flow in the mold. Drying of plastic resin can be a key step in the injection molding process, since too much moisture can cause a number of processing problems. advantages 8. It is. If splay is occurring in the same place on each part, identify where in the flow front the splay is generated. Purchase Injection Molding Components now. Except for polyolefins (common examples being polyethylene and polypropylene), materials need to be dried before they are injection molded. Air, water vapor, and decomposition gas are all components of gas, and the presence of gas is the primary cause of this mark. If the only solution is to use a spray, try our Tuff-Kote and Dri-Kote high-performance mold-release sprays. The Troubleshooter’s notebook. The injection speed has a great impact on the degree of molecular orientation in the component and therefore influences the shrinkage and the development of a joint line. This can be avoided by running the resin through a dryer prior to molding. Unfortunately, fixing this injection molding defect often requires mold reformatting. If the material contains moisture，it should be dried; if decomposition or depolymerization are causing the volatiles, the cylinder temperature should be lowered, and if moisture in the mould is to blame, its temperature should be. A Guide To Polyolefin Injection Molding Introduction Polyolefins are the most widely used plastics for injection molding. A. Here are 3 common injection molding flaws and how to prevent them from happening in the future: Flow Lines. Since the cavity is more than 90% full, not much more plastic is needed. Injection Molding Processing Guide. The material supplier is the best source for this information. 39 sec, is about 2000 psi-sec. It is a cosmetic defect typically appearing as an off-color streak, often silver in hue, along the. FOW takes care of all manufacturing tasks in house thus we are able to offer you an accuracy range within 0. The J-ADS Superior series machine offers unmatched shot-to-shot consistency and incredible reliability. Participating in DFM and mold flow analysis is a good way to achieve this. Gas Marks Defined. Adding other internal lubricating aids to the amides may also provide adequate mold release for a given molding. COLD SLUG WELL – Space provided directly opposite the sprue opening in an injection mold to trap the cold slug. Splay. These materials have been developed to meet specific requirements for strength, high temperature and chemical resistance, abrasion resistance and low friction. Injection Molding Flash Occur Causes. Splay can be a costly problem in the production of your molded components. Step 3 – Examine the Defective Part and Rule Out Obvious Causes. The moisture and volatile content in the raw material is. There only needs to be a very tiny amount of water in the material for steam to form during molding. Injection Molding Know How. 1 Overview of Splay Defect Splay affects. When two materials can’t bond together, it results in separation that very quickly becomes delamination. There is a level of insulation from the plastic layer on the wall. 1. Troubleshooting Guide for Injection Molding. Excessive injection speed causes turbulent, non-laminar melt flow into the cavity. 025 inches per inch, depending on the particular resin, molding conditions, part design, part wall thickness, and direction of flow. Answer: The trapped gas ignites from the heat generated by pressure. Plastic injection molders – whether lacking the experience, adept knowledge or proper equipment – can produce defective products that don’t stand up to industry regulations, appearance requirements, and/or general client. Splay: A layer/ streak of a unwanted gaseous byproduct from the melt or moisture in the material comes in between the melt flow and the cavity walls preventing the texture from being picked up and in addition eventually leaving a residue: Dry plastic to suggested moisture levels; Decrease injection speeds; Decrease melt temperatureWith ABS injection molding, you get the collective benefits and properties of three monomers. Identifying your injection molded part defects is the first line of defense against wasting valuable molding machine time. Heat-related: Check that the melting temperature is. 508-520-0011 Fax: +1. The wet material can cause the formation of steam, creating pockets of trapped gas. gas, possibly resulting in inconsistent shot sizes and splay. How to Avoid Silver Streaks and Splay Marks in Plastic Injection Molding: Sink marks are a common issue in injection molding that occur when there are variations in wall thickness. Add more cooling circuits. Many defects can occur in injection molding. 5: l. Silver Streak Analysis & Troubleshooting (1). On the other hand, with injection-molded products, various conditions—including the proportions and dispersion of material and additive contents, the temperature used to melt the plastic, the pressure, and the cooling time—significantly affect quality. The three main causes of splay are heat, moisture, and shear. Slower, controlled speeds allow for smoother laminar flow that prevents air entrapment. It provides a clear, free-flowing path for plastic granules, powders, and liquids (such as liquid color) into the feed section of the screw. Due to Microsoft's end of support for Internet Explorer 11 on 15/06/2022, this site does not support the recommended environment. Splay Can Holder; Mold Maintenance. A purge compound can be a great solution before pulling the tool. This article continues our series of troubleshooting reports from one of the leading on-the-spot problem solvers in the molding industry. He can be reached at (414) 369-5555, Ext. Too cold in the rearInjection Molding of Multimaterial Systems. A mold is filled under pressure with the molten material, then cooled to form a solid part before being removed from the mold. Gate blush is a molding defects commonly caused at the gate location of molded part, It shows as rings or ripples in the mold cavity surrounding the gate area. How to Prevent Common Failure Modes in Injection Molding. The defect detection tool then identifies any anomalous parts, detecting both functional and cosmetic defects. Increase the mold temperature. Those who look for splay to check for moisture will be fooled. As mentioned above, the gate size is a measuring act between filling the mold exactly and keeping the smallest runner possible to improve shearing when the mold cycles in the machine. Adjust improve product quality such as removing blush, splay, flash, short shots and resolving. While not always visible, weld lines (aka knit lines) are where two resin flows meet. The faster the injection speed, the worse the jetting. High injection speeds lead to shear splay since the material is exposed to high shear conditions. 1. The material supplier is the best source for this information. building; 35 molding machines;Injection molding Troubleshooting guide. Custom Plastic Injection Molding - Troubleshooting Techniques - For this part of this series, we will start out with a very basic injection molding problem and some possible ways of solving it. Molten polymer moves through the barrel of the machine and forced in to a steel mold. There are many "lookalike" defects, and more possible cause of splay, including excessive mold lubrication. Valve gate hot runner nozzles were introduced to the injection molding industry shortly after the first hot runner systems appeared on the market. 6 sec instead of the typical 7 sec for ABS/PC. The goal is to correctly identify which problem is actually causing the defect. Increase gate size; 2. 00. Figure 1 presents the shrinkage of polypropylene versus wall thickness in injection molded parts. A reduction of 10 – 25% is usually achieved in. What is Splay? Silver or white streaks appearing on the surface of the part often indicate splay in injection molding. Splay can be a costly problem in the production of your molded components. The problem could be the result of machine settings made before the gate was installed. 3 is a part tested 16 hr after molding. Fundamentals of Scientific Injection Molding Seminar: Hands-on, Setup, Processing & Troubleshooting (Cleveland) $ 1,595. This time we’re going to take a look at Splay. 7 Million Products, 2,000 Brands. Date: October 23, 2019. Must Have 3 YRS Experience In Plastic Injection Molding & Submit a Resume . Brittleness can be defined as the tendency of a molded plastic part to break or crack under conditions in which it would not normally do so. He has provided process-engineering expertise to many top companies, including Glock, Honda, Johnson Controls, and. Flow marks are most commonly caused by resin cooling too quickly or improper gate location. Use the data to calculate relative shear rates and relative viscosities: Relative Shear Rate = 1 ÷ fill time. 4. Injection. Learn how to identify the. e Fill, Pack, Hold & Cooling/Plastication. Appearance. Injection molding Troubleshooting guide Eastman copolyesters. Relative Viscosity = Hydraulic pressure x intensification. com and a consultant/trainer in plastic injection molding. What Are Silver Streaks in Injection Molding? A silver streak, also known as a splay mark, is a cosmetic defect that is typically visible on plastic parts with a smooth surface. Air flow may become erratic due to moisture in the molding system and this can be a source of trouble. 2) Vents in an injection mold should let the air out, but not the liquid plastic. In addition, it is important to note that nylon is not only affected by poor drying/ moisture conditions. Injection molding offers numerous advantages when it comes to producing HDPE parts, such as cost-effectiveness, high customization, and high malleability. High nozzle temperatures can promote the formation of thermal splay marks from keeping the. Many companies worldwide continue to purchase China injection molding services; some are placing large orders, and some even set up their own sourcing office in China. Splay Can Holder; Mold Maintenance. Scientific molding practices optimize gate velocity for bubble-free filling. In reality, to ensure that every product comes out of the process a success takes a lot of skill and knowledge. Practical Injection Molding. This is an excerpt from Lesson #6 in Paulson's Injection Molded Part Problems and Solutions training progam - Splay (or Silver Streaks) and how to fix them. Dyi-Cheng Chen. 21 Splay Three types of splay are often encountered in injection molding. Issues that can occur include splay marks. To decide on the likely cause(s), test each to prove/disprove whether it is causing the splay, then take the corrective action. Black specks, splay, color swirls, brown streaks are all molding issues that can often be attributed to poor purging. 2. It can be caused by mold lubrication, material, process, or machine issues. (2-3) High viscosity / low fluidity. A Plastic Injection Molding Process Problem – Troubleshooting Methods . Gas will mix with plastic melt if the high. Splay A defect in the surface of a molded part that is usually small in size, shiny, and may have the appearance of a lightly tinted or silver streaks. Figure 1 presents the shrinkage of polypropylene versus wall thickness in injection molded parts. CPT offers new & rebuilt injection mold machine replacement barrels, screws, & tips at competitive costs. 3. This cosmetic defect occurs in plastic injection molding, when silver or white streaks appear on the surface of the part face due to air, contamination, heat, moisture, or shear issues. The weld line can either be a minor cosmetic issue. Adjust resin and cooling temperatures. 508-520-3222 Jan 04, 1999.